If by o ring you mean the ring on the plastic cap that allows you to access the filter, than nothing but remember to do it next time.
No, they are not. If you ask for an oil change they will change the engine oil & filter. They will not change the transmission fluid unless you ask for it.
Yes , you can change the filter only and either prefill the oil filter OR top up the engine oil , but if you have already started the engine the " dirty " oil has mixed with the new oil
yes
You CAN change the oil filter by itself and then top up the oil , but it's best to change both in the long run
Yes , if you want to , and then top up the engine oil ( but in the long run it's best to change both )
By changing the engine oil, that covers it.
ANS1Yes, but this is not recommended. You will lose some oil in the process of changing the filter, so check your oil before you start the engine and add what is needed.ANS2I suggest that you always change the filter before you change the oil. Change the filter with the oil still in the crankcase, that way if the new filter doesn't fit you can put the old filter back on and drive back to the parts store to exchange the filter for the right one. If you change your oil first, the new oil will be contaminated by the old oil in the filter if you have to put it back on to drive the car to get the right filter.As Ans1 says, it is not recommended to change the filter without changing the oil. You are changing the oil, not because the oil is dirty, but because it is chemically changed by use and will not properly protect your engine.
Yes, you can change only the filter and then add enough oil to replace the amount lost by removing the filter.
yeap.
if I understand your ? can not changing an old oil filter gasket casue damage to your engine NO only if it leaked out all the oil other wise no. If the filter change was the cause of the leak and you lost enough oil for the engine to start clattering, yes, it caused the permanent engine damage.
Either the cap is cracked, which you will need a new one from the dealer. Or you forgot the o ring when installing the new filter
its the same process as changing synthetic oil, except you use regular oil.